1. Field of the Invention
The present invention relates to an inkjet recording method and, more particularly, to an inkjet recording method employing an undercoat liquid and a colored liquid.
2. Description of the Related Art
Inkjet systems, in which ink is discharged as droplets from an ink discharge orifice, are employed in many printers for reasons such as small size, low cost, and an ability to form an image without contacting a recording medium. Among these inkjet systems, a piezo inkjet system, in which ink is discharged by utilizing deformation of a piezoelectric element, and a thermal inkjet system, in which droplets of ink are discharged by utilizing the phenomenon of boiling of the ink by means of thermal energy, are characterized by their high resolution and high speed printing properties.
In recent years, inkjet printers have not been limited only to photographic printing and document printing for home use or office use, and the development of commercial printing equipment and industrial printing equipment employing inkjet printers has been carried out.
In contrast to conventional inkjet inks and inkjet recording methods for home use or office use, there is a strong requirement for inkjet inks and recording methods intended for use in commercial printing equipment or industrial printing equipment to have (1) wide color reproduction in a formed image, (2) an ability to carry out printing on all types of recording media including nonpermeable recording media such as plastic media, and (3) an ability to carry out high speed printing employing a single pass system.
Inkjet inks and inkjet recording methods for home use or office use have often been developed for the purpose of printing photographs or documents, and there is the serious problem of their narrow color reproduction as commercial or industrial printed materials.
Furthermore, when recording is carried out on a non-absorbing recording medium by use of conventional inkjet inks and inkjet recording methods, it takes a long time for drying of the fired droplets or penetration thereof into the recording medium, there are the practical problems that the image easily spreads, and there is mixing of adjacent ink droplets on the recording medium, thereby preventing a sharp image from being formed. Moreover, as another problem of an image recorded on a non-absorbing recording medium, fixation of the image is not good, with the result that it is easily peeled off from the recording medium and the abrasion properties are poor.
Furthermore, as a problem when applied to high speed printing employing the single pass system, uneven color, etc. occurs due to fired droplet interference. ‘Fired droplet interference’ means a phenomenon in which, since liquid droplets fired next to each other coalesce and move, they are displaced from the positions at which they landed, thus causing nonuniformity in line width when drawing fine lines and causing uneven color, etc. when drawing a colored surface.
As a method for solving the above-mentioned problems, various techniques have so far been proposed. As an example thereof, there is a method in which a radiation-curable undercoat is provided, and during curing a colored image is formed thereon (ref. e.g. JP-A-2000-141616 (JP-A denotes a Japanese unexamined patent application publication)).
Furthermore, in order to achieve a desired color gamut, a radiation-curable inkjet ink employing a special pigment such as Pigment Orange or Pigment Green has been disclosed (ref. e.g. JP-PCT-2003-531223 (JP-PCT denotes a published Japanese translation of a PCT application)).
As an attempt to impart high definition drawing performance when printing at high speed, two reactive liquid inks are used, and they are reacted on a recording medium; for example, there have been disclosed a method in which, after a liquid containing a basic polymer is applied, recording is carried out using an ink containing an anionic dye (ref. e.g. JP-A-63-60783), and a method in which, after a liquid composition containing a cationic substance is applied, an ink containing an anionic compound and a colorant is applied (ref. e.g. JP-A-8-174997).
Furthermore, as an ink for which fixation to a nonpermeable medium is taken into consideration there has been proposed an inkjet recording method in which a UV-curing ink is used, dots of the UV-curing color ink discharged onto a recording medium are irradiated with ultraviolet rays that match the discharge timing, thus pre-curing them to such a degree that the viscosity increases and adjacent dots do not mix together, and they are then further irradiated with ultraviolet rays and fully cured (ref. e.g. JP-A-2004-42548).
Moreover, there has been proposed a technique in which, after a radiation-curable white ink is applied uniformly on a transparent or semi-transparent non-absorbing recording medium as an undercoat layer and solidified or made to have an increased viscosity by exposure to radiation, inkjet recording is carried out using a radiation-curable color ink set, thus improving the color ink visibility, spreading, and the problem that images vary between various recording media (ref. e.g. JP-A-2003-145745). Furthermore, there has also been proposed a technique in which, instead of the radiation-curable white ink above, a substantially transparent actinic radiation-curable ink is applied by an inkjet head (ref. e.g. JP-A-2005-96254).